As the title states this truck stalls when you’re cruising above 60mph in 5th gear about 80% of the time once you shift to neutral or engage the clutch. Some background…the owner of this truck bought it and shipped it to a very reputable shop in CO. They spent a year putting in a rebuilt 2F, H55, all new interior, rust correction and some paint work. It’s. 1985 and very clean. This shop de-smogged the motor as well. Once he had it shipped back to TX it started falling on its face. The de-smog is not the traditional one I’ve (and most folks) used from the sticky in this section. It’s bare bones as they did not keep the HAC, fuel cut sensor and some of the vac lines were in the wrong place. I had to flat bed the truck to my shop. Sorted out what was left there post the de-smog, discovered the original carb was put back on the rebuilt 2F. Pulled the carb and had @mattressking rebuild it. I also blew out a very restricted fuel feed line along the frame. New soft lines on both the feed/return lines. New fuel filter. I’ve inspected the tank twice via the sending unit port and it’s very clean. Also did the aftermarket fuel canister upgrade from Autozone. Truck was running awesome for several months. Then the owner noticed in June (about the time he was starting to hit the Hwy with the AC on) it shutting off when he would coast to a stop light after cruising at Hwy speeds. I’ve checked for vac leaks with carb cleaner with no luck. Vac gauge holds steady at 17 (at idle). @matressking has walked me through several tests and it’s passed all. Then I swapped another recent rebuilt carb off this owners other 60 to this truck and it does the exact same thing. Instead of removing it a second time I just plugged the carb from this 60 in question onto his other 60 and it does not stall. Back to the issue…when the truck stalls I’ve pulled over several times and the float bowl is at the correct level. And the motor fires right back up and runs awesome. At least until you remove the load on the drivetrain at hwy speeds with the AC on. Nate and I have talked at length and leaning towards a decrease in the spark at that moment when you’ve been traveling at speed and engage the clutch. I swapped out the AC amplifier
